This invention relates to a novel device adapted to the carbonation of aqueous beverages at the point of consumption. Carbonation is accomplished by contacting the beverage to be carbonated with "molecular sieves", i.e., crystalline aluminosilicates, which contain adsorbed gaseous carbon dioxide. Carbon dioxide is released from the molecular sieves by displacement with water from the beverage solution. The liberated carbon dioxide is then dissolved into the liquid to form the carbonated beverage. The molecular sieves are bonded into a monolithic structure having sufficient surface area for contact between the aqueous beverage to be carbonated and the molecular sieves so as to provide means for a ready displacement of the carbon dioxide to be released by water from the beverage solution.
Commercial beverage carbonation usually involves carbon dioxide-liquid contact under pressure with intensive mixing in a cooled container. Such commercial methods, of course, require elaborate and sophisticated equipment not available at the point of beverage consumption.
Several simple carbonation techniques which are suitable for home use have been disclosed in the art. Most commonly, such prior art carbonation systems utilize a chemical "couple" to generate carbon dioxide in situ within the beverage to be carbonated. Such a couple usually consists of the combination of an inorganic carbonate such as sodium bicarbonate and an edible food acid such as citric acid or a acid-acting ion exchange resin. Contact between compounds of this type in an aqueous solution results in the formation of gaseous carbon dioxide and the salt of the food acid. Several patents (Mitchell et al., U.S. Pat. No. 3,241,977, issued May 22, 1966; Mitchell et al., U.S. Pat. No. 3,467,526, issued Sep. 16, 1969; Hovey, U.S. Pat. No. 3,492,671, issued Jan. 27, 1970; and Hughes, U.S. Pat. No. 2,742, 363, issued Apr. 17, 1956) describe preferred embodiments of such acid-bicarbonate or acid resin-bicarbonate systems in detail. All of these methods, however, result in the formation of undesirable off-tasting organic salts in solution or require utilization of complex ion exchange material to prevent these salts from dissolving in the beverage. Such salts are particularly noticeable and objectionable to the consumer when formed in substantial amounts in achieving relatively high levels of carbonation.
Another home carbonation technique utilizes dry beverage compositions containing water-reactive carbonic acid anhydrides which release CO.sub.2 or H.sub.2 CO.sub.3 in aqueous solution, for example, see U.S. Pat. No. 3,441,417, issued Apr. 29, 1969, to Feldman et al. These compositions, however, require rather complex formulation and, in many instances, require incorporation of a buffering system into the beverage solution.
Thus, it has been proposed in co-pending patent application Ser. No. 302,149, filed Oct. 30, 1972, now issued as U.S. Pat. No. 3,888,998, June 10, 1975, which is a continuation-in-part of application Ser. No. 200,849, filed Nov. 22, 1971 now abandoned, that aqueous beverages could be advantageously carbonated at the point of consumption with the use of an effective amount of a crystalline aluminosilicate molecular sieve material having adsorbed therein at least about 5% by weight of carbon dioxide. Molecular sieves of the types used in carbonating beverages at the point of consumption are crystalline aluminosilicate materials of the following general formula: EQU M.sub.2/n O:SiO.sub.2 :aAl.sub.2 O.sub.3 :bH.sub.2 O
in the salt form, where M is a metallic cation, ordinarily Na or K with other cations substituted possibly by exchange, n is the valence of said metal cation M, a is the number of moles of alumina and b is the number of moles of water of hydration.
Upon removal of at least some of the water of hydration by heating , or "firing", the crystalline aluminosilicates become highly porous and are characterized by a series of surface cavities and internal pores which form an interconnecting network of passageways within the crystal. As used herein, the term "firing" means heating in a kiln or by other suitable means so as to at least partially remove the water of hydration from the bodies to be fired. It specifically excludes vitrification of said bodies. Such dehydrated molecular sieves are often referred to as "activated" meaning that they are ready to adsorb carbon dioxide or other available molecules. Due to the crystalline nature of such materials, the diameters of the surface cavities and of the internal pores are substantially uniform and of molecular magnitude. For this reason, the crystalline aluminosilicates have found wide use in the separation of materials according to molecular size or configuration, hence the name "molecular sieves" .
Carbonation in accordance with the latter-named method necessitates contacting the molecular sieves with the beverage liquid. Generally, the molecular sieves loaded with CO.sub.2 are placed in a container, and the liquid to be carbonated is then added in sufficient amount to cover the sieves. Heretofore, in copending application Ser. No. 302,149, referred to above, as U.S. Pat. No. 3,888,998, carbonation has been accomplished by utilizing a multiplicity of small molecular sieve agglomerates, such as produced following the teachings of U.S. Pat. No. 2,973,327, issued Feb. 28, 1961, to William J. Mitchell et al., or by utilizing a solid disk of compressed molecular sieves. The agglomerates are typically either spherical in shape, commonly known as beads, or roughly cylindrical in shape, commonly known as pellets.
The use of a multiplicity of molecular sieve agglomerates, however, is disadvantageous due to the disadvantages inherent in using the small particles. Since the molecular sieve agglomerates are not in themselves designed for internal consumption, the molecular sieve bodies must be enveloped or otherwise constrained so as to be readily separable from the liquid beverage upon consumption. These various encasements of the molecular sieve bodies may have economical, aesthetic, or other disadvantages which preclude their use for commercial marketing purposes. A composite molecular sieve body would overcome many of these disadvantages inherent in the use of a multiplicity of small agglomerates. However, there are severe technical problems in formulating a suitable monolithic structure. A solid molecular sieve disk, or tablet, made from either compressed molecular sieves or from a mixture of aluminosilicates bonded together with a clay mineral binder tends to be unsatisfactory in that these bodies have encountered problems when used for carbonating liquid beverages. In order to obtain sufficient carbonation of the aqueous beverage, that is, both a sufficient amount of CO.sub.2 released into the beverage and a minimal rate of CO.sub.2 generation to maintain the beverage in a carbonated state, the molecular sieves must have adsorbed therein at least a certain amount of CO.sub.2. However, when these solid disks which contain an effective amount of gaseous carbon dioxide are placed in the liquid beverage environment, the pressure generated by the carbon dioxide release from the molecular sieves is often so extreme as to cause disintegration or destruction of the disk body. If precautions are taken to prevent this, specifically, using a binder composition which imparts sufficient strength to the composite body so as to maintain its structural integrity, then the binder causes a decrease in the rate of release of the carbon dioxide. This can result in either unacceptably low carbonation levels or unacceptably long carbonation times.
Accordingly, it is an object of the present invention to formulate a rigid composite molecular sieve body which, when adsorbed with an effective amount of carbon dioxide, will satisfactorily carbonate an aqueous beverage without the destruction or dissolution of said composite molecular sieve body.
It is also an object of this invention to provide bonded molecular sieve disks which effectively carbonate a beverage in a commercially acceptable time period.
It is a further object of the instant invention to provide simple but effective devices for point of consumption beverage carbonation. These and other objects readily apparent to those skilled in the art will be apparent from the disclosure and appended claims.